In a sensor such as a position sensor and each type of in-vehicle sensors (a throttle sensor, a pedal sensor, and a vehicle height sensor) and a resistor such as a potentiometer and a trimmer, a slider 100 is used for transmitting and receiving such as an electrical signal and power between a substrate member on a main body side of the sensor and an assembly rotating or moving straight with respect to the main body side substrate (FIG. 1). The slider 100 includes a brush type contact material 10 of which ends are slidingly contacted with a rotor of the sensor. Multiple pawls 11 curved at around a contact point with the substrate are connected in the brush type contact material 10. An end of each pawl 11 is used in a state coming into slidingly contact with the substrate to be contacted, and therefore a pawl end 11a preferably slidably moves as smooth as possible.
In manufacture of a brush type contact material, first a sliding contact piece (see FIG. 2), which is flat and not curved, is manufactured by punching by press. On this occasion, punching often produces burrs around a pawl end of a brush by, and thereby sharpening the end. If the burrs remain in the pawl end, the pawl end does not smoothly slide, and therefore, an end of a punched sliding contact piece is normally formed in a curved shape.
Barrel polishing was once used as a method for forming, in a curved shape, an end portion of a punched sliding contact piece. The barrel polishing is a method in which abrasive media such as grind stones and pressed sliding contact pieces are put in a container, and the overall periphery of the sliding contact pieces are polished by rotation of the container. The barrel polishing is an effective means capable of polishing multiple small-sized sliding contact pieces at the same time. However, the barrel polishing is not a method for intensively polishing a specific portion and is not suitable to certainly curve a surface of an end portion. Also, a polishing state is likely to vary.
An applicant of the present application proposes a manufacturing method using a laser beam and a contact material manufactured by the manufacturing method with respect to a method for manufacturing a brush type contact material by the above barrel polishing. This manufacturing method is a method in which pawl ends of pressed sliding contact pieces are melted and coagulated by sequential irradiation with a laser beam. In this manufacturing method, a curved surface processing can be performed only to pawl ends, and also a material with a constant quality without variations can be effectively manufactured through setting an appropriate laser beam irradiation conditions. In a brush type contact material manufactured by this method, a pawl end has a balanced curved surface shape such as a sectional arc-like shape, has a smooth surface, and enables a smooth sliding movement.